Small business Server 2003 not upgrading

I am trying to upgrade my small business server 2000 box and when it starts to upgrade and gets going i get the follwoing error "unable to create, modify, etc the c:\winnt.sif file" i have looked at my root C drive and cannot find it? Any ideas why SBS 2k3 is looking for that. From what i have read it's for unattended installations which i am not doing. Any ideas greatly appreciated. Thanks!